326 MOTOR RESPONSES 



of those in the oral groove. If this is true, it is evident that the responses 

 in this form must be associated with internal changes. 



The fact that in specimens with the longitudinal axis directed ob- 

 liquely to the direction of the current, the entire end nearest the cathode 

 is affected, and the fact that the size of the portion affected varies directly 

 with the strength of the current, indicates not only that the current re- 

 sults in a functional division of the organism (as maintained by Ludloff, 

 Verworn, and Koehler), but also that whatever the factors involved 

 may be, they act on a structure which is well distributed through the 

 entire body and which is located some distance below the surface — 

 probably the neuromotor apparatus. For only in a structure which is 

 some distance from the surface, could a current produce the same changes 

 in the distribution of substances on the anodal and the cathodal sides 

 of the portion affected, resulting in reversal in the direction of the 

 stroke in all the cilia on this portion. 



It is well known that momentary reversal in the stroke of the cilia 

 can be induced in Paramecium by almost any sudden environmental 

 change (Jennings, 1906), and that more prolonged reversal can be in- 

 duced by transfer from culture fluid to distilled water or from distilled 

 water to solutions of monovalent cation salts, but not usually by transfer 

 to solutions of bivalent cation salts (Mast and Nadler, 1926; Oliphant, 

 1938) . These changes, therefore, produce the same result as is produced 

 by an electric current on the cathodal surface, indicating similarity in 

 action. 



Greeley (1904) maintains that paramecia drift toward the anode, i.e., 

 that they are negatively charged, indicating that there is a negative layer 

 at the surface. Statkewitsch (1903) observed that if one end is directed 

 toward the anode and the other toward the cathode, the former shrinks 

 and the latter swells, indicating that the more solid substance is negative 

 in relation to the more fluid substance. If all this obtains, a direct cur- 

 rent will result in a decrease in the concentration of the positive, or an 

 increase in the concentration of the negative ions on the cathodal side of 

 the surface of the organism and on each semipermeable structure within. 

 There will also be a decrease in the concentration of the negative, or an 

 increase in the concentration of the positive ions on the opposite side. As 

 a result, water will drift toward the cathodal side, and the solid particles 

 will drift in the opposite direction. 



